1. Field of the Invention
The present invention relates to an apparatus for controlling the concentration of a liquid toner in a recording apparatus, and more particularly to an apparatus which is adapted to control the concentration of a liquid toner to be constant.
2. Description of the Related Art
In a recording apparatus employing a liquid toner, for example, an electrostatic recording apparatus, the concentration of a toner in the liquid toner largely influences the quality of recorded images, and therefore the toner concentration is required to be constant. However, since a sensor for directly measuring the toner concentrations is expensive, it is quite rare to measure the toner concentration to automatically control the same in conventional electrostatic recording apparatus.
Generally, as recording operations are performed, toner particles included in a liquid toner used for the recording operation are gradually decreased, which results in making the toner concentration lower. When image data having a large number of dot signals representing an image to be recorded is applied to an electrostatic recording apparatus, the recording apparatus records an image formed by the toner on a recording medium in the form of a large number of dots corresponding to the dot signals. There has been therefore proposed, for example in JP-A-62-144184 and JP-A-63-174362 (UM), an apparatus which counts the number of dot signals included in the image data or measures the image length as recorded and automatically supply an amount of enriched toner liquid corresponding to the number of the counted dots or the measured image length to a liquid toner.
However, since the liquid toner generally employs a volatile solvent, the concentration of the liquid toner is influenced not only by an amount of consumed toner but also by an amount of evaporated solvent. It is therefore quite difficult to correctly adjust the concentration of the liquid toner only by counting the number of dot signals included in the image data to supply the toner in accordance with the counted number of the dot signals.